1. Field of the Invention
The present invention relates to a pigment multimer, a coloring composition, and a cured film using the same. The present invention further relates to a color filter having a cured film, a method for manufacturing a color filter, a solid-state imaging element having a color filter, and an image display device.
2. Description of the Related Art
As one of the methods for manufacturing a color filter which is used for a liquid crystal display device, a solid-state imaging element, or the like, there is a pigment dispersion method. As the pigment dispersion method, there is a method for manufacturing a color filter by a photolithography method by using a coloring photosensitive composition which is obtained by dispersing pigments in various photosensitive compositions. That is, a curable composition is applied onto a substrate by using a spin coater, a roll coater, or the like, the substrate is dried to form a coating film, and the coating film is developed by pattern exposure, thereby obtaining colored pixels. This operation is repeated for the number of the desired hues to manufacture a color filter.
The method is stable with respect to light or heat due to a use of pigments, and positional accuracy is sufficiently secured since patterning is performed by a photolithography method. Accordingly, the method has been widely used as a method suitable for manufacturing a color filter for color display, or the like.
Meanwhile, in recent years, there has been a demand for a color filter for a solid-state imaging element such as a CCD to have high definition. As the definition of the color filter is heightened, the pattern size tends to be decreased, but it is considered that the pigment dispersion method which has been widely used in the related art has difficulty in further improving resolution while also decreasing the pattern size. One of the reasons therefor is that coarse particles generated due to the aggregation of pigment particles cause color unevenness in a fine pattern. Accordingly, the pigment dispersion method which has been widely used so far has been in a recent situation where it has not necessarily been used for purposes requiring a fine pattern, such as in a solid-state imaging element.
In the related art, a color filter has been manufactured using a pigment as a coloring agent, but use of a dye instead of a pigment is under examination. In the case of using the dye, the points shown below particularly become problems.
(1) A dye is generally inferior to a pigment in terms of light fastness and heat resistance. In particular, there is a problem in that optical characteristics are changed due to a high-temperature process performed at the time when a film is formed of indium tin oxide (ITO) which is widely used as an electrode of a liquid crystal display or the like.
(2) Since a dye tends to inhibit a radical polymerization reaction, there is difficulty in designing a coloring photosensitive composition in a system using radical polymerization as curing means.
Particularly, in the case where a photolithography method is used for the manufacture of a color filter, the following points become problems.
(3) Since an ordinary dye exhibits low solubility in an aqueous alkaline solution or an organic solvent (hereinafter simply referred to as a solvent), it is difficult to obtain a coloring photosensitive composition having a desired spectrum.
(4) A dye interacts with other components in a coloring photosensitive composition in many cases, and thus, it is difficult to regulate the solubility (developability) of exposed and unexposed areas.
(5) In the case where the molar absorption coefficient (s) of a dye is low, it is necessary to add the dye in a large amount. As a result, amounts of other components in a coloring photosensitive composition, such as a polymerizable compound (monomer), a binder, and a photopolymerization initiator, have to be relatively reduced, and curability of the composition as well as heat resistance, developability, and the like of the cured composition deteriorate.
Due to these problems, it has been difficult so far to form a colored pattern which is constituted with a fine and thin film for a high-definition color filter and has excellent fastness by using a dye. Further, in the case of a color filter for a solid-state imaging element, a colored layer is required to be formed of a thin film of 1 μm or less. Accordingly, in order to obtain desired absorption, a large amount of a pigment needs to be added to a curable composition, and as a result, the aforementioned problems arise.
Furthermore, for a coloring photosensitive composition including a dye, it is pointed out that in the case where a heating treatment is carried out after forming a film, a phenomenon of color migration easily occurs between different hues of colored patterns adjacent to each other or between layers disposed and stacked on each other, in addition to color migration, there are also problems in that a pattern is easily peeled off in an area with a low exposure dose due to decrease in sensitivity; since the amount of photosensitive components contributing to photolithographic properties is relatively reduced, an intended shape or color density cannot be obtained due to heat sagging or elution caused at the time of development; and the like.
As methods for solving such problems, methods for resolving the problems by polymerizing a pigment have been suggested (see, for example, JP2012-32754A, JP2007-138051A, JP2000-162429A, and JP2003-246935A).